Sulfur Compounds in the Environment

Abstract

A new analysis method for sulfur compounds using solid phase microextraction (SPME), gas chromatography (GC) and pulse flame photometric detector (PFPD) has been developed in this study. In the method, air samples were collected with Tedlar air sampling bags, Carboxen-Polydimethylsiloxane (Carboxen-PDMS) coated fibers were then used to extract analytes from the samples and introduce them into the injector of a GC by thermal desorption. The analytes were separated using a GS-GasPro column and detected with the PFPD. Using a SPME-GC-PFPD method the retention times of 28 sulfur compound standards were determined for the identification of sulfur compounds in air samples. A method was also developed for the quantification of H2S. The reproducibility (<14%),lowest quantitation limit (4 ppb for H2S) and detection limit (0.4 ppb for H2S) were determined for this method. Emissions from geothermal sources, wetlands and wastewater treatment works are the sources of atmospheric sulfur compounds. Rotorua (New Zealand),a beach near Point England (Auckland, New Zealand) and a wastewater treatment plant were selected for sampling. With the SPME-GC-PFPD method COS, H2S, CS2, SO2, (CH3)2S were identified in the air in residential areas in Rotorua. COS, H2S, CS2, SO2, CH3SH, (CH3)2S and CH3(CH2)2CH2SH were identified in the air around geothermal sources in Rotorua, three additional compounds, C2H5SH, CH3CH2CH2SH and CH3CH2SCH3 were identified in a fumarole emission. It was observed that the H2S concentrations in residential areas were well below the air quality standard for geothermal areas (0.05 ppm) at the time of collection, but the H2S concentrations in the vicinity of geothermal areas were above the standard. COS, H2S, CS2, CH3SH, (CH3)2S, (CH3)2S2, and SO2 were identified in the air in a wastewater treatment plant. As low concentrations of sulfur compounds were detected in the open air they did not cause any odour problems to the workers or the public. It was observed that the H2S concentrations in the open air were below the air quality standard (0.005 ppm) for non-geothermal areas. PM10 samples collected from Hunua, Hamilton and Christchurch in New Zealand, were analysed using a modified SPME-GC-PFPD method. H2S, SO2, CH3SH, (CH3)2S, (CH3)2S2, thiophene and ethyl methyl sulfide were identified in the particulate samples. The concentration of each sulfur compound identified in the samples varied between the three locations, which might have been caused by different emission sources. The newly developed SPME-GC-PFPD trace level analysis method for sulfur compounds and H2S is fast, easily operated, cost effective and reliable. In this study, the applications of this method have been used to demonstrate its versatility for the analysis of sulfur containing samples in various matrices.